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99 Explorer ? about tires

06-25-2018, 09:35 PM
Do all the tires have to be same size since it all wheel drive up to a certain speed. I don't want to ruin tranny.

06-25-2018, 09:42 PM
Yes, with AWD you want the tires to be the same size and inflated to the pressure listed on the door placard, which likely calls for the same pressure front and rear. It won't be the transmission that will be damaged if the tires are different sizes, but rather the transfer case with the viscous coupling unit (VCU).


06-26-2018, 08:40 AM
Not only do the tires have to be the same size, they also should be the same make and model and state of wear. That way the rolling diameters are as close as possible. Doing otherwise could damage the the tranny.

As a side note: There are no regulations saying that a tire of a certain size has to be of certain dimensions. So tires made by different manufacturers might have quite different rolling diameters.

06-27-2018, 12:51 AM
yeah tell me about it i have a 2008 escape 4wd that is awd and it just cost me 3100 dollars to have the transmission rebuilt along with the transfer case all because the person before me was too cheap to put all the same type of tire on the vehicle and i have 2 winter tires and 2 all season just waiting to put 4 tires on it before i can drive it, it is just sitting as i cannot afford to get the tires but will be able to after summer

08-07-2018, 02:49 AM
Ok, I changed tires & now when i'm driving at slow speed 0 to 45 mph the steering wheel jerks & the whole front end feels like a busted belt in a tire but there are no belts broke. I did find that the sway bar link bushings are gone on both sides. Could this be causing my problems? Also can you tell me how to disable the 4 wheel drive? Is there a fuse or relay under the hood that I can take out?

08-07-2018, 08:02 AM
4WD and AWD are not the same thing. In your original post you mention the truck if AWD. If that's the case, there is not a way to disable the AWD. If your truck is 4WD there will be a switch that allows you to select different modes. If one of those modes is 2WD, then you can easily disable the 4WD.

Is the steering wheel "jerk" a repetitive jerk or is it more random, such as when you hit a bump? I would expect the damaged anti-sway bar end links to cause a noise on bumps but not to cause a physical jerking sensation. But, quite honestly, if the bushings are shot there very well could be other parts up front (ball joints, tie rod ends, suspension bushings) that are also shot and causing looseness in the front end.

Also, you could try swapping the wheels and tires front to rear to see if the sensation changes. You could still have a tire issue that is just not visually apparent.


08-11-2018, 03:50 PM
I'm sorry, I haven't been on here in a few days. I switched the tires front to rear, Now the rear is wobbling, So one of the tires has to be bad! + the jerking in the steering stopped. It is 4 wheel drive. Also I unplugged a little square black box on the frame beside the transfer case & the thumping stopped & the 4x4 still works when I flip the switch.
Thanks for the help.

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